Abstract: Objective: The effects of agar oligosaccharides on the quality characteristics of Litopenaeus vannamei were investigated during frozen storage. Method: Fresh L. vannamei were immersed in distilled water, 1.5% and 3.0% agarose oligosaccharides, 1.5% and 3.0% sodium tripolyphosphate solution, respectively. The thawing loss rate, cooking loss rate, pH, L^* value, water activity, water content, texture characteristics, myofibrillar protein content, Ca²⁺-ATPase activity, carbonyl content, chemical bond content, active sulfhydryl content and total sulfhydryl content were measured on the 0, 20, 40, 60, 80, and 100 d of frozen storage. The results showed that with the increased frozen storage time, the cooking loss rate, thawing loss rate, L^* value, carbonyl content and hydrophobic bond content of L. vannamei increased by 14.52%~37.66%, 35.33%~71.01%, 4.98%~17.71%, 78.96%~142.72% and 156.58%~271.23%, respectively. The springiness, chewiness, water activity, water content, myofibrillar protein content, ionic bond content, hydrogen bond content, active sulfhydryl group, and total sulfhydryl group content decreased by 24.47%~50.49%, 39.56%~66.05%, 2.13%~4.67%, 4.13%~10.08%, 15.30%~25.33%, 46.32%~66.50%, 31.79%~66.83%, 41.97%~60.77% and 30.29%~44.84%, respectively. The pH showed a trend of decreasing first and then increasing. Among them, the results of each index in the agar oligosaccharide and sodium tripolyphosphate groups were better than those in the distilled water group, and the effect was the best when the concentration was 3%. Conclusion: Agar oligosaccharides can significantly inhibit the deterioration of muscle quality of L. vannamei during frozen storage. This study provides ideas and theoretical support for the development and application of new phosphorus-free antifreeze.